(a) Body Mass Index (BMI) is based on measured or self-reported height and weight, For more information see Body Mass Index inGlossary (Health).(b) Excludes persons for whom measured or self-reported height or weight data was not available.(c) Proportions have been age standardised to the 2001 Australian population to account for differences in the age structure of the population over time.

Source: ABS data available on request, Australian Health Survey. ABS data available on request, National Health Survey.

COMMENTARY

OVERWEIGHT AND OBESITY

In 2011-12, a higher proportion of males aged 18 years and over were overweight or obese (70%) than were females (56%). These overweight/obesity rates were up five and six percentage points respectively on the 1995 results. These estimates are based on people's measured height and weight and have been age standardised to account for differences in the structure of the population over time.

People being overweight or obese may have significant health, social and economic impacts, and is closely related to lack of exercise and to diet. Being overweight or obese increases the risk of suffering from a range of health conditions, including coronary heart disease, Type 2 diabetes, some cancers, knee and hip problems, and sleep apnoea.(Endnote 1)In 2008, the total annual cost of obesity to Australia, including health system costs, loss of productivity costs and carers' costs, was estimated at around $58 billion. (Endnote 2)

While genetics may play a role in a person's propensity to become overweight or obese, the fundamental cause is an imbalance between energy consumed and energy expended. Shifts towards energy-dense diets and decreasing physical activity are two of the factors that have contributed to increases in rates of overweight and obesity.(Endnote 3)

Over the last two decades, there has been a steady shift in the Australian population towards the higher end of the Body Mass Index (BMI), driven mainly by weight gain rather than by changes in height. The BMI, a simple index of weight for height, is commonly used to classify people as overweight and obese. It is defined as the weight in kilograms divided by the square of the height in metres (kg/m2).

By age

In 2011-12, the rate of overweight/obesity for males 18 years and over was significantly higher than females for all age groups except 18-24 year olds and those 75 years and over.

In general, rates of overweight/obesity increase with age. In 2011-12, 18-24 year old males and females had the lowest rates (42% and 35% respectively). Rates then increased, peaking for males between 45 and 74 years of age (at around 80%), and between 55 and 74 years of age for females (at around 70%). For males, the rate then declined to around 69% after 75 years of age.

Between 1995 and 2011-12, there were significant increases in the rate of overweight/obesity for a number of male and female age groups. For males this included 25-34 year olds (up 7%), 35-44 year olds (up 8%) and males 75 years and over (up 7%). For females, this included 18-24 year olds (up 9%), 35-44 year olds (up 10%) and 45-54 year olds (up 7%).

Self-reported BMI was collected in the 2001, 2004-05 and 2007-08 National Health Surveys. Measured BMI was collected in the 1995 and 2007-08 National Health Surveys, and the 2011-12 Australian Health Survey. The 2007-08 survey was therefore the only time where both measured and self-reported BMI were collected. When comparing the two measures in 2007-08, self-reported rates of overweight/ obesity were significantly lower. For instance, 63% of males and 48% of females self-reported a BMI that would classify them as overweight or obese, compared to 68% of males and 54% of females using the measured item.

Overweight and obesity in children is a major health concern. Studies have shown that once children become obese they are more likely to stay obese into adulthood and have an increased risk of developing both short and long-term health conditions, such as Type 2 diabetes and cardiovascular disease. (Endnote 4)

In 2011-12, around a quarter of all Australian children aged 5-17 years (24% of boys and 27% of girls) were either overweight or obese according to measured BMI. Since 1995, the proportion of obese boys in the 5-12 year age group increased significantly by three percentage points to 7%. For girls, there was a significant increase in the 13-17 year age group classified as overweight (up 6 percentage points to 18%).

Overweight and obesity in Aboriginal and Torres Strait Islander peoples

In 2004-05, 62% of Aboriginal and Torres Strait Islander males and 58% of Aboriginal and Torres Strait Islander females aged 18 years and over were overweight or obese. For both Aboriginal and Torres Strait Islander males and females, the rates for overweight/obesity were higher in older age groups, with nearly three quarters of both the male and female populations aged 55 years and over being overweight or obese.